Reconfigure and Extend Existing Wireless Network

You minimally need a wireless ethernet bridge.

<-- wireless (to isp) -->[wireless ethernet bridge](lan)<-- wire -->(wan)[wireless router]<-- wireless (to your clients) -->

The wireless ethernet bridge just substitutes for what would normally be a wired connection to your cable/dsl modem. The router doesn't really care, it just wants to get an IP assignment from the ISP and assign it to the WAN port.

Alternatively, you could use a wireless repeater, but only one that supports UNbridged wireless connections (for security reasons).

<-- wireless (to isp) -->[wireless repeater (unbridged)]<-- wireless (to your clients) -->

Just as with the wireless ethernet bridge, you connect to the ISP via wireless, but this time the router creates a “virtual” firewall between that wireless connection and the wireless signal it repeats to the clients on your local network. If that wireless repeater has an integrated switch (or you add a switch), those wired clients would have access as well, and be likewise protected. In effect, you’ve created a wireless router that connects to the ISP via wireless rather than using a wire and physical WAN port. But you need it to be UNbridged so it replaces the firewall that was previously provided by the (now absent) WAN port.

Whichever method you choose, I suggest using a dd-wrt compatible router, which supports both wireless ethernet bridge and (unbridged) wireless repeater. Wireless ethernet bridge is probably the easiest and most straightforward solution for most ppl, but wireless repeater has the advantage of eliminating an every device.

Of course, you can also buy a standalone wireless ethernet bridge or (unbridged) wireless repeater, but they tend to be relatively expensive compared to using a dd-wrt compatible router. A dd-wrt router solves this type of problem very nicely. But ultimately the choice is yours.